A photovoltaic electrochemical cell converts light energy into electrical energy, the “photovoltaic effect” being the process through which light energy is converted into electrical energy. Photovoltaic cells are typically solid state devices, usually semiconductors such as silicon. Usually one or more photosensitive junctions are irradiated, simultaneously generating a voltage and a current.
A potentially lower cost alternative to the solid state devices are dye-sensitized cells. Dye-sensitized solar cells offer a promising route to low cost solar energy. A standard dye-sensitized cell uses a liquid electrolyte to complete the electrical circuit between the convoluted surface of the dye-sensitized electrode and the flat counter electrode. A liquid is normally necessary to fill all the microscopic voids in the dye-sensitized electrode and thereby provide an effective ion conduction path to each dye molecule, where the light is absorbed and energy converted into electronic form. However cells made with the conventional liquid electrolyte suffer from a risk of leakage, variable thickness and ‘pooling’ in flexible cells, and, in some formulations, loss of volatile components by diffusion and evaporation, all of which can be detrimental to the reliability and longevity of the cell.
WO03/023890 describes hydrophilic polymers for use in a membrane electrode assembly formed by an in situ polymerisation process. WO2005/020332 describes the use of these materials in photovoltaic electrochemical cells. This publication further describes a method of forming both MEAs and membranes having improved photovoltaic properties. The contents of both of these publications are incorporated herein by reference.
UK unpublished application number 0900568.7, incorporated herein by reference, describes the use of encapsulation methods as a route to incorporating components into membrane electrode assemblies (MEAs), when those components inhibit polymerisation. An example is to provide an iodide/-tri-iodide system encapsulated for later release into a solid electrolyte to allow in situ curing of the MEA.